Mantaflow bake fluid from command line, "NameError" : not defined
Baking Mantaflow (fluid) from command line works now. However, thus far, only with Blender 2.83+.

https://developer.blender.org/rBa50c131a0d71d04915cc39c5a412f4f16c6f706b :

"The issue was the usage of the global __ main __ Python module.
When running scripts in the text editor, Blender would overwrite
the __ main __ module."



Thanks to Ichlubna! ..and the many kind devs.